A look into the future: diagnosis of cancer through blood analysis
Today I will tell you about a topic that is gaining relevance in the field of cancer diagnosis. As you have already heard thousand times, in order to cure a tumor efficiently, it needs to be diagnosed at the earliest possible stage. This means that it should be detected prior to metastasize (to spread around the body) and prior to become too big, preventing thus the possibility to remove it surgically.
A branch of cancer research is dedicated to the development of novel diagnostic methods to detect cancer at early stage, in a rapid, cheap and non-invasive way. Nowadays tumors are usually diagnosed by imaging techniques (magnetic resonance, endoscopies, X-ray, PET and so on), biopsies and other laboratory tests. These ways are all valid, but some of them don’t have enough sensitivity (which means that they would not detect the presence of the tumor at early stage), others are invasive (no one likes to undergo biopsies or endoscopies, right?).
A novel diagnostic technique, which is advancing together with the biological and genetic knowledge of tumors, is the analysis of circulating cell-free DNA (cfDNA).
What is the circulating cell-free DNA?
Usually DNA is kept in the nucleus of the cell in the same way money is kept in the caveau of a bank. When a cell dies, DNA is released and fragmented in small pieces, and subsequently degraded together with all the components of the dead cell. Part of it, anyway, is dispersed in the blood circulation. Here comes the name of circulating cell-free DNA.
The presence of cfDNA in the plasma fraction of the blood is a physiological condition, which means that there are always DNA fragments circulating, derived from dead cells. Cells that remain in the center of the tumor mass do not get enough nutrients and oxygen, therefore they die at higher rate. Because of this, initially it was thought that the amount of cfDNA increased only in the presence of a tumor, but later it was discovered that also other conditions, including autoimmune diseases, lead to similar increases.
How can we use cfDNA to detect the presence of a tumor?
I described here how a normal cell can become a tumor cell. Briefly, some bricks of the DNA wall are mutated. But this is not the only difference: DNA from tumor cells presents some other small features that allow to distinguish it from the “normal” DNA. All these DNA variations (in sequence and other features) differ from tumor to tumor, and when it will be possible to catalog all (or most) of them, it will be possible to do a quick and non-invasive test on a blood sample to verify the presence of cfDNA from tumor cells. Sensitivity of this test would be very high, making it possible to detect the presence of tumor at a very early stage.
The direction is to develop tests which will allow to screen blood samples for the presence of cfDNA of any tumor at once. This will allow to detect the rising tumor and also to understand to which genetic class it belongs to, in order to address the precision therapy in the right direction.
The way is marked, now we just have to support research and wait.